n.外壳；坚硬的外壳；面包皮

vt.盖以硬皮

vi.结硬皮

The earth's crust is layered.. 地球的外壳是分层的。

The crust on the snow was thick enough for us to walk on it. 外层的雪已经冻硬，可以在上面行走。

Please cut the bread into slices and remove the crust. 请将面包切片并去除外壳。

The crust of the bread is burnt. 这块面包的外皮烤焦了。

The snow crusted the lake last night. 昨夜的雪使湖面结了冰。

The snow may crust at night, due to outward radiation. 由于外部辐射，晚上雪可能结成雪壳。